1. Field of the Invention
The present invention relates to tires for use on wheels of farm working machines and, more particularly, to a tire having a tread integrally formed with a plurality of lugs.
2. Background Information
A tire for farm working machines, which generally need a great tractive force, has a tread formed with a plurality of lugs. Japanese Patent Laid-Open Publication No. HEI-6-57487, for example, presents a farm working machine wheel having a plurality of lugs formed obliquely on the tread. Japanese Utility Model Laid-Open Publication No. HEI-7-30401 presents a farm working machine wheel with a plurality of lugs protruded outward from lateral edges of a tire.
FIGS. 10A and 10B hereof illustrate the wheel disclosed in HEI-6-57487.
A farm working machine wheel 200 shown in FIGS. 10A and 10B consists of a tire 201 and a rim 206 supporting the tire 201. The tire 201 has a tread 205 on which long lugs 202 and short lugs 203 are circumferentially disposed in an alternating manner, slanting at a predetermined angle θ with respect to the wheel rotation axis.
The tread 205 of the tire 201 has a convexly curved shape as shown in FIG. 10B. The long lugs 202 and the short lugs 203 slant with respect to the wheel rotation axis line. When the farm working machine wheel 200 travels on farm land having a soft upper layer, the soft soil is likely to be expelled in arrow directions. The wheel 200 thus sinks down, reaching hard soil in a lower layer, and obtaining a driving force. If the sinking amount of the wheel 200 is large, a lower body portion of the farm working machine mounted with the wheel 200 contacts the ground, having difficulty in smooth traveling.
FIGS. 11A and 11B hereof illustrate the wheel disclosed in HEI-7-30401.
A farm working machine wheel 210 shown in FIGS. 101A and 11B has a plurality of lugs 213 formed on a tubular portion 212 of a tire 211. Each of the lugs 213 consists of a circumferential lug 214 extending circumferentially about the tire 211 and an axial lug 215 extending from the circumferential lug 214 in parallel with the rotation axis of the tire 211. Specifically, the axial lug 215 protrudes outward from a lateral edge of the tubular portion 212. Reference numeral 217 denotes a core material of the tire 211.
The tubular portion 212 of the tire 211 of the farm working machine wheel 210 has a small width, causing the wheel 210 to be likely to sink in the soil. The farm working machine has difficulty in smooth traveling, as described with FIGS. 10A and 10B.
It is thus desired to improve a farm working machine wheel to prevent sinking of the wheel and to improve the traveling performance of the farm working machine on soft land or cultivated land.